MIG (metal inert gas), TIG (tungsten inert gas) and stick-welding processes all readily weld grade 304 stainless steel if you use the proper electrode. The welding electrode needs to match the composite of the 304 stainless steel as close as possible to provide an adequate weld that will not crack. Electrodes for 308 stainless steel welding closely match the composite of the 304 stainless and are widely available for all the popular welding processes. When using the MIG and TIG welding processes, you will also need to use a shielding gas meant for stainless steel, which means argon for TIG and trimix shielding gas for MIG.
Put on safety glasses.
Follow the MIG welder operating manual to install the 308 stainless steel welding wire.
Close the MIG welder feeder rolls, turn on the MIG welder and depress the trigger of the MIG gun to feed the stainless steel wire through the lead of the MIG gun.
Clip the excess wire that protrudes from the tip of the MIG gun with the wire cutters. Ensure that you leave only about 1/2 inch of wire sticking past the end of the MIG gun welding tip.
Secure the bottle of trimix welding gas to the MIG welder; crack open, then close, the valve located on the top of the tank to clear obstructions from the valve, and attach the flow meter to the bottle of shielding gas.
Set the wire speed and voltage of the MIG welder as specified on the welding guide chart located inside the MIG welder.
Put on your welding helmet and welding gloves.
Align the pieces of stainless steel that need to be welded, leaving at least a 1/16-inch gap between the pieces to allow the stainless steel to move. Holding a 1/16-inch weld gap is important to keep the metal from warping while you weld the pieces together.
Place the end of the welding wire into the weld joint that you fit in the previous step, lower you welding hood and hold the trigger of the MIG gun for two seconds to place a tack weld in the weld joint. Repeat the process to place a tack weld every 1/2 inch along the entire weld joint.
Realign the welding wire protruding from the MIG gun with one edge of the weld joint, lower your welding helmet and depress the trigger of the MIG gun to finish the weld joint. Keep the same speed as you travel along the weld joint to evenly distribute the heat in the 304 stainless steel.
Allow the weld joint to cool to room temperature and then clean the weld bead with the wire brush.